Hydraulic lift truck



March 9, 1965 e. F. QUAYLE 3,172,339

HYDRAULIC LIFT TRUCK Filed Oct. 2, 1962 2 Sh t 1 INVENTOR @copst' F Quayc 477 UQ/VEY March 9, 1965 a. F. QUAYLE 3,172,339

HYDRAULIC LIFT TRUCK Filed Oct. 2, 1962 2 Sheets-Sheet 2 INVENTOR.

Gsogsc F QUAYLE United States Patent '0 3,172,339 HYDRAULIC LIFT TRUCK George F. Quayle, Philadelphia, Pa., assignor, by mesne assignments, to Yale & Towne, Inc., New York, N.Y., a company of Ohio Filed Oct. 2, 1962, Ser. No. 227,780 12 Claims. (Cl. 92-61) This invention relates to a lift truck incorporating a vertically extending lift ram having at least two telescoping pistons.

In a truck of this type, it is important that the load carriage of the truck is not moved too rapidly by the ram in the elevated position because of the less stable condition of the truck in this position of the load carriage. However, with rams as heretofore proposed and used, this is not possible without the use of special controls for controlling the speed of the ram. This is due to the construction of such rams which results in the inner piston having a substantially smaller effective area and therefore, a substantially higher speed, than the outer piston.

The purpose of this invention is to provide a lift truck having a lift ram in which the effective area of the inner piston closely approaches that of the outer piston, with a resulting decrease in the difference in speed between the pistons so that special speed controls are not necessary.

This is accomplished in accordance with the invention by a novel arrangement of the fluid seal between the cylin der and outer piston and a novel stop arrangement for limiting extension of the inner piston relatively to the outer piston.

Other objects and advantages of the invention will become apparent from the following description when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a perspective view of a lift truck incorporating a lift ram constructed in accordance with the invention, showing the ram and uprights collapsed.

FIG. 2 is a perspective view, similar to that of FIG. 1, showing the lift ram extended to lift the load carriage and extensible uprights of the truck; and

FIG. 3 is a sectional view of the lift ram showing the details of the construction thereof.

Referring to the drawings and in particular to FIGS. 1 and 2, a lift ram 10, constructed in accordance with the invention, is shown incorporated in a lift truck T. The truck T includes primary uprights 11 secured to the truck, secondary uprights 12 mounted for vertical movement on the primary uprights, tertiary uprights 13 mounted for vertical movement on the secondary uprights 12, and a load carriage 14 mounted for vertical movement on the tertiary uprights.

As best shown in FIG. 2, the lift ram includes an outer cylinder 15, a first telescoping tubular piston 16 slidably mounted within the cylinder 15, and a second telescoping piston 17 slidably mounted in the tubular piston 16. The cylinder is supported on the secondary uprights 12 at 18, and a pair of sheaves 19, best shown in FIG. 1, are mounted on the outer end of the inner piston 17.

A pair of lift chains 20 are secured at one end to the load carriage 14, extend over the sheaves 19 which are secured to the top of the inner piston 17, extend down around a pair of sheaves 21 which are secured to the secondary uprights 12 adjacent the lower ends thereof, and are secured at the opposite ends to the top of the primary uprights 11. When the ram 10 is first actuated, both the pistons 16 and 17 extend together relatively to the cylinder 15 and the load carriage 14 is first moved through the chains 20 to the top of the tertiary uprights 13, while the uprights remain in the collapsed position. Thereafter, an continued operation of the ram 10, the tertiary 3,172,339 ?atented Mar. 9, 1965 uprights 13 are raised relatively to the secondary uprights 12 through the load carriage 14 and chains 20, and the secondary uprights 12 raised relatively to the primary uprights 11 through the chains 20 which extend over the sheaves 21, until the carriage and uprights reach the fully extended position as shown in FIG. 2. It will be appreciated that movement of the load carriage 14 and uprights in the elevated position is effected by the extension of the inner piston 17 relatively to the extended outer piston 16.

Referring now to FIG. 3, the cylinder 15 of the ram 10 is conveniently formed from a length of tubing 22 which is closed at the lower end by a cap or head 23 which is welded, or otherwise secured thereto. The opposite or upper end of the tubing 22 has a collar member 24 threaded, or otherwise secured thereto, which is prevented from accidental removal by locking screws 25.

The collar member 24 is provided with an annular recess 26 which carries suitable packing 27 for forming a sliding fluid seal between the upper end of the cylinder 15 and the outer surface of the piston 16. The packing 27 is compressed by an annular collar or nut 28 which is threaded into the outer end of the recess 26, and the nut 28 carries a suitable wiping ring 29 which also slidably engages the outer surface of the piston 16.

The piston 16 is conveniently formed from a length of tubing 30 having an annular guide member 31 threaded, or otherwise secured, to the lower end. The annular guide member 31 has an outer diameter substantially less than the inner diameter of the cylinder 15 so that ample clearance, indicated at 32, is provided between the inner surface of the cylinder 15 and the outer surface of the guide member 31 to provide a passage permitting free flow of fluid between opposite sides of the guide member 31. The packing 27 carried by the collar member 24, therefore, forms the sole fluid seal between the cylinder 15 and the tubular piston 16, and as the fluid pressure can act on both sides of the guide member 31, the effective diameter which determines the area on which the fluid pressure acts to extend the piston 16, therefore, is the outer diameter of the tube member 30 of the piston 16, indicated by the dimension D in FIG. 3. Extension of the outer piston 16 relatively to the cylinder is limited by engagement of an outwardly extending stop surface 31a on the guide member 31 with opposed, inwardly extending stop surface 24a on the collar member 24.

The outer end of the tubing 30 of the pitson 16 is provided with a collar member 33 which is threaded on the outer end thereof and prevented from accidental removal by lock screws 34. The collar member 33 is provided with an annular recess 35 which carries suitable packing 36 for forming a sliding fluid seal with the outer surface of the innermost piston 17. The packing 36 is compressed by an annular nut member 37 which is threaded into the outer end of the recess 35. The nut member 37 carries a suitable wiping ring 38 which slidably engages the outer surface of the piston 17.

The inner piston 17 is conveniently formed from a length of tubing 39 having an annular guide member 40 threaded on the lower end, and a head member 41 threaded in the upper end. A fluid seal is provided between the head member 41 and the inner surface of the tubing 39 of the innermost piston 17 by a suitable sealing ring 42 carried by the inner end of the head member 41. The outer end of the head member 41 is provided with a stud 43 through which a bracket 44 for supporting the sheaves 19 is secured to the innermost piston 17.

The annular guide 40 guides the inner end of the inner piston 17 during extension thereof relatively to the outer piston 16. Clearance may be left between the outer surface of the guide member 40 and the inner surface or bore of the outer piston 16 so that the bore of the outer piston does not have to be accurately machined and finished. The packing 36 carried by the outer end of the outer piston 16 forms the necessary sliding fluid seal between the inner piston 17 and the outer piston 16.

Ideally, the innermost piston 17 has an outer diameter equal to the inner diameter of the outer piston 16. However, because of the difliculty in making the inner piston 17 of exactly the same outer diameter as the inner diameter of the outer piston 16 and to avoid costly machining and finishing of the bore of the outer piston 16, the inner piston 17 may be made slightly smaller in diameter than the outer piston 16 so that a slight clearance, indicated at 45 in FIG. 3, is left between the outer'surface ofthe inner piston 17 and the inner surface of the outer piston 16. This clearance, however, may be very small, less than a tenth of an inch, and for all intents and purposes, the outer diameter of the inner piston 17 is substantially equal to that of the inner diameter of the outer piston 16. The effective diameter of the inner piston 17 which determines the area on which the fluid pressure acts-in extending the inner piston 17 relatively to the piston16, therefore, is the diameter of the outer surface of the inner piston 17, indicated by the dimension d in FIG. 3. The diflerence in the effective areas of the piston 17 and the outer piston 16 is, therefore, very small with the result that there is very little difference in the speed of the two pistons.

It will be appreciated that with this dimensional relationship between the inner piston 17 and the outer piston 16, the guide 40 which guides the inner end of the inner-piston 17 in the outer piston 16, cannot be of sufficient diameter to provide a stop surface to limit extension of the inner piston 17 relatively to the outer piston 16, as is the case in the guide 31 which is secured to the inner end of the outer piston 17, and provides a stop surface 31a. This problem, however, is solved through a novel limit stop arrangement, which in the particular form disclosed, includes a tubular member 46 which extends upwardly within the inner piston 17 and has a stud member 47 secured to the upper end and an annular member 48 secured to the lower end thereof. A stop member or nut 49 is threaded on the stud 47 and'provides a stop surface 50 engageable witha stop surface 51 formed on a portion of the guide member 40 which extends inwardly of the outer surface of the piston 17. The annular member 48 secured to the lower end of the member 46 in turn provides a stop surface 52 which engages an inwardly directed shoulder 53 formed on the guide member 31 of the outer piston 16.

Thus, when the inner piston 17 is extended relatively to the outer piston 16, the stop surface 51 on the guide member 40 of the inner piston 17 engages the stop surface 50 on the nut member 49, and the stop surface 52 on-the member 48 engages the stop shoulder 53 on guide member 31 of the outer piston 16 to limitextension of the inner piston 17 relatively to the outer piston 16. The stop arrangement between the inner piston 17 and the outer piston, therefore, is within the outer surface of the inner piston 17, allowing the inner piston 17 to have an outer diameter substantially equal to thatof the inner diameter of the outer piston 16.

Fluid under pressure is introduced into the cylinder 15 to extend the pistons 16 and 17 through a passage 54 formed in the head member 23 which communicates with a passage 55 through athreaded nipple 56 formed integrally with the inner surface of the head 23. A conventional flow regulator valve 57 is threaded on'the nipple 56. The flow regulator valve 57 allows free flow of fluid into'the ram, while limiting the speed of flow out of the ram to prevent the uprights and load carriage of the truck from being lowered too rapidly in the event there is a failure in one of the hydraulic hoses connecting the rams with the source of fluid pressure.

When fluid under pressure is first introduced into the cylinder 15 through the passages 54 and 55, the fluid pres- 4 sure acts on the effective area determined by the outside diameter D of the outer piston 16 to extend both the pistons 16 and 17 together relatively to the cylinder 15. Openings 58 may be provided in the annular member 48 to facilitate flow of fluid to the pistons.

It will be appreciated that the surface finish of engaging sufaces between the member 48 and the head 23 and shoulder 53 is sufficiently rough to allow the fluid to freely pass between these surfaces.

This movement of the pistons 16 and 17 is transmitted through the lift chains 20 to lift the load carriage on the uprights and to then lift the extensible uprights 12, 13,'as previously described. The extension of the two pistons 16 and 17 together as a unit continues until stop surface 31a on the guide 31 on the outer piston 16 engages the stop surface24a on the collar 24of the cylinder 15 to stop further extension of the piston 16. Thereafter, fluid pressure acts on the effective areadetermined by the outer diameter d of the inner piston 17 to extend the inner piston 17 relatively to the outer piston 16. Extension of the inner piston 17 relatively to the extended outer piston 16 lifts the load carriage and uprights to the fully extended position shown in FIG. 2. While the speed of the ram is slightly higher as the inner piston 17 is extended relatively to the outer piston 16, the difference in speed is very slight, because of the small difference in effective areas of the pistons, and special controls are not necessary for controlling the speed of the ram during movement of the load carriage in the elevated position. i

As the inner piston 17 extends relatively to the extended outer piston 16, the stop surface 51 on the guide 40 on the inner end of the piston 17 engages the stop surface 51) on the nut member 49 so that the tubular member 46 is carried with the piston 17. The tubular member 46 is carried by the inner piston 17 until the stop surface 52 on the member 48 which is secured to the lower end of the member 46 engages the shoulder 53 on the guide 31 of the extended outer piston 16 to stop further extension of the inner piston 17 relatively to the extended outer piston 16. At this point, the load carriage 14 and uprights 12 and 13 are in the extended position as shown in FIG. 2.

From the preceding description, it can be seen that there is provided a lift truck incorporating a two piston lift ram in which the difference in speed between the two pistons is so slight that special controls for controlling the speed of the ram are not necessary. Furthermore, because the inner piston has an outer diameter throughout the length thereof which is substantially the same as the inner diameter of the outer piston, the ram has greater strength under axial loads and greater resistance to lateral buckling and bending.

While one embodiment of the invention has been shown and described, it will be appreciated that this is for the purpose of explanation and illustration, and that changes and modifications may be made therein without departing from the spirit and scope of the invention.

I now claim:

1. In a lift truck having vertical uprights and a load carriage mounted for vertical movement on said uprights,

a vertically extending ram'for lifting said load carriage on said uprights, said ram having an outer cylinder, a tubular piston slidably received within said cylinder, and an inner piston slidably received within said tubular piston, said inner piston having an outer diameter substantially the same as the inner diameter of the tubular piston, and

stop means positioned within an opening in the inner end of the inner piston and cooperating with means. secured to said inner piston within said opening and. with means on' the inner end of said tubular piston to limit extension of said inner piston relatively to said tubular piston.

2. In alift truck having vertical uprights and a load carriage mounted for vertical movement in said uprights,

a vertically extending ram for lifting said load carriage on said uprights, said ram having an outer cylinder, a tubular piston slidably received within said cylinder, and an inner piston slidably received within said tubular piston, said inner piston having an outer diameter substantially the same as the inner diameter of said tubular piston, and

stop means within the outer surface of said inner piston and operatively connected to the inner end of said tubular piston, and stop means secured to said inner piston within the outer surface thereof and cooperating with said stop means connected to the inner end of said tubular piston to limit extension of said inner piston relatively to said tubular piston.

3. In a lift truck having vertical uprights and a load carriage mounted for vertical movement on said uprights,

a vertically extending ram for lifting said load carriage on said uprights, said ram having an outer cylinder, a first tubular piston slidably received within said cylinder, and an inner tubular piston slidably received within said first tubular piston, said inner piston having an outer diameter substantially the same as the inner diameter of said first tubular piston, and

stop means positioned within said inner tubular piston and cooperating with means secured to said inner tubular piston within the outer surface thereof and with means on the inner end of said first tubular piston to limit extension of said inner piston relatively to said tubular piston.

4. In a lift truck having vertical uprights and a load carriage mounted for vertical movement on said uprights,

a vertically extending ram for lifting said load carriage on said uprights, said ram having an outer cylinder, a first tubular piston slidably received within said cylinder, and an inner tubular piston slidably received within said first tubular piston, said inner piston having an outer diameter substantially the same as the inner diameter of said first tubular piston, and

an elongated member extending Within said inner tubular piston, stop means on the outer end of said elongated member cooperating with stop means on the inner end of said inner tubular member, and stop means on the inner end of said elongated member cooperating with stop means on the inner end of said first tubular piston to limit extension of said inner tubular piston relatively to said first tubular piston.

5. In a lift truck having vertical uprights and a load carriage mounted for vertical movement on said uprights,

a vertically extending ram for lifting said load carriage on said uprights, said ram having an outer cylinder, a tubular piston slidably received within said cylinder, and an inner piston of substantially the same diameter throughout the length thereof slidably received within said tubular piston, said inner piston having an outer diameter substantially the same as the inner diameter of said tubular piston,

fluid seal means secured to the outer end of said cylinder and slidably engaging the outer surface of said tubular piston, said fluid seal means forming the sole fluid seal between said tubular piston and cylinder,

fluid seal means between said tubular piston and said inner piston,

cooperating stop means on said cylinder and said tubular piston for limiting extension of said tubular piston relatively to said cylinder, and

stop means within the outer surface of said inner piston and operatively connected to the inner end of said tubular piston, and stop means secured to said inner piston within the outer surface thereof and cooperating with said stop means connected to said tubular 5. piston to limit extension of said inner piston relatively to said tubular piston. 6. In a lift truck having vertical uprights and a load carriage mounted for vertical movement on said uprights,

a vertically extending ram for lifting said load carriage on said uprights, said ram having an outer cylinder, a tubular piston slidably received within said cyl inder, and an inner piston of substantially the same diameter throughout the length thereof slidably received within said tubular piston, said inner piston having an inner diameter substantially the same as the inner diameter of said tubular piston,

fluid seal means secured to the outer end of said cylinder and slidably engaging the outer surface of said tubular piston, said fluid seal means forming the sole fluid seal between said tubular piston and cylinder,

fluid seal means between said tubular piston and said inner piston,

cooperating stop means on said cylinder and said tubular piston for limiting extension of said tubular piston relatively to said cylinder, and

stop means positioned within an opening in said inner piston and cooperating with means secured to said inner piston within said opening and with means in the inner end of said tubular piston to limit extension of said inner piston relatively to said tubular piston.

7. In a lift truck having vertical uprights and a load carriage mounted for vertical movement on said uprights,

a vertically extending ram for lifting said load carriage on said uprights, said ram having an outer cylinder, a first tubular piston slidably received within said cylinder, and an inner tubular piston of substantially the same diameter throughout the length thereof slidably received within said first tubular piston, said inner tubular piston having an outer diameter substantially the same as the inner diameter of said first tubular piston,

fluid seal means secured to the outer end of said cylinder and slidably engaging the outer surface of said first tubular piston, said fluid seal means forming the sole fluid seal between said tubular piston and cylinder, I

fluid seal means between said first tubular piston and said inner tubular piston.

cooperating stop means on said cylinder and said first tubular piston for limiting extension of said first tubular piston relatively to said cylinder, and

stop means Within said inner tubular piston and operatively connected to the inner end of said first tubular piston and stop means secured to said inner tubular piston within the outer surface thereof and cooperating with said stop means connected to said first tubular piston to limit extension of said inner tubular piston relatively to said first tubular piston.

8. In a lift truck having vertical uprights and a load arriage mounted for vertical movement on said up- (3() rights,

a vertically extending ram for lifting said load carn'age on said uprights, said ram having an outer cylinder, a tubular piston slidably received within said cylinder, and an inner piston slidably received within said tubular piston, said inner piston having an outer diameter substantially the same as the inner diameter of said tubular piston,

fluid seal means secured to the outer end of said cylinder slidably engaging the outer surface of said tubular piston,

fluid seal means between said tubular piston and said lnner piston,

inwardly extending stop means on the outer end of said cylinder and an outwardly extending member on the inner end of said tubular piston which cooperates with said stop means on said cylinder to limit extension of said tubular piston relatively to said cylinder.

passage means communicating with both sides of said outwardly extending member on said tubular piston to allow free flow of fluid between both sides of said outwardly extending member, and

cooperating stop means on said tubular piston and said inner piston for limiting extension of said inner piston relatively to said tubular piston.

9. In a lift truck having vertical uprights and a load carriage mounted for vertical movement 011 said uprights,

a vertically extending ram for lifting said load carriage on said uprights, said ram having an outer cylinder, a first tubular piston slidably received within said cylinder, and an inner tubular piston slidably received within said first tubular piston, said inner tubular piston having an outer diameter substantially the same as the inner diameter of said first tubular piston,

fluid seal means secured to the outer end of said cylinder slidably engaging the outer surface of said first tubular piston,

fluid seal means between said first tubular piston and said inner tubular piston,

inwardly extending stop means on the outer end of said cylinder and an outwardly extending member on the inner end of said first tubular piston which cooperates with said stop means on said'cylinder to limit extension of said first tubular piston relatively to said cylinder,

passage means communicating With both sides of said outwardly extending member on said first tubular piston to allow free flow of fluid between both sides of said outwardly extending member, and

cooperating stop means on said first tubular piston and said inner piston for limiting'extension of said inner tubular piston relatively to said first tubular piston.

10. In a lift truck having vertical uprights and a load carriage mounted for vertical movement on said uprights,

a vertically extending ram for lifting said load carriage on said uprights, said ram having an outer cylinder, a tubular piston slidably received within said cylinder, and an inner piston of substantiallythe same diameter throughout the length thereof slidably received within said tubular piston, said inner piston having an outer diameter substantially the same as the inner diameter of said tubular piston,

fluid seal means secured to the outer end of said cylinder and slidably engaging the outer surface of said tubular piston, Said fluid seal means forming the sole fluid seal between said tubular piston and said cylinder,

fluid seal means secured to the outer end of said tubular piston and slidably engaging the outer surface of said inner piston, said fluid seal meansforming the sole fluid seal between said tubular piston and said inner piston,

cooperating stop means on said cylinder and said tubular piston for limiting extension of said tubular piston relatively to said cylinder, and

stop means within the outer surface of said inner piston and operatively connected to the inner end of said tubular piston, and stop means secured to said inher piston within the outer surface thereof and cooperating with said stop means connected to said tubular piston to limit extension of said inner piston relatively to said tubular piston.

11. In a lift truck having vertical uprights and a load carriage mounted for vertical movement on said uprights,

a vertically extending ram for lifting said load carriage on said uprights, said ram having an outer cylinder, a tubular piston slidably received within said cylinder, and an inner piston of substantially the same diameter throughout the length thereof slidably received within said tubular piston, said inner piston having an outer diameter substantially the same as the inner diameter of said tubular piston,

fluid seal means secured to the outer end of said cylinder and slidably engaging the outer surface of said tubular'piston, said fluid seal means forming the sole fluid seal between said tubular piston and said cylinder,

fluid seal means secured to the outer end of said tubular piston and slidably engaging the outer surface of said inner piston, said fluid seal means forming the sole fluid seal between said tubular piston and said inner piston,

cooperating stop means on said cylinder and said tubular piston for limiting extension of said tubular piston relatively to said cylinder, and

stop means-positioned within an opening in saidinner piston and cooperating with means secured to said inner piston within said opening and with means on the inner end of said tubular piston to limit extension of said inner piston relatively to said tubular piston.

12, In a lift truck having vertical uprights and a load carriage mounted for vertical movement on said uprights,

a vertically extending ram for lifting said load carriage on said uprights, said ram having an outer cylinder, a first tubular piston slidably-received within said cylinder, and an inner tubular piston of substantially the same diameter throughout the length thereof slidably received within said first tubular piston, said inner tubular piston having an outer diameter substantially the same as the inner diameter of said first tubular piston,

fluid seal means secured to the outer end of said cylinder and slidably engaging the outer surface of said first tubular piston, said fluid seal means forming the sole fluid seal between said first tubular piston and said cylinder,

fluid seal means secured to the outer end of said first tubular piston and slidably engaging the outer surface of said inner tubular piston, said fluid seal means forming the sole fluid seal between said tubular piston andsaid inner piston,

cooperating stop means on said cylinder and said first: tubular piston for limiting extension of said first tubular piston relatively to said cylinder, and

stopmeans within said inner tubular piston and operatively connected to the inner end of said first tubular piston, and stop means secured to said inner tubular piston within the outer surface thereof and cooperating with said stop means connected to said first tubular piston to limit extension of said inner tubular piston relatively to said first tubular piston.

References Cited by the Examiner UNITED STATES PATENTS 1,424,233 8/22 Berry 925l 2,830,563 4/58 Bur'ckhalter 925l 2,887,092 5/59 Brady 925l RICHARD B, WILKINSON, Primary Examiner, 

1. IN A LIFT TRUCK HAVING VERTICAL UPRIGHTS AND A LOAD CARRIAGE MOUNTED FOR VERTICAL MOVEMENT ON SAID UPRIGHTS. A VERTICALLY EXTENDING RAM FOR LIFTING SAID LOAD CARRIAGE ON SAID UPRIGHTS, SAID RAM HAVING AN OUTER CYLINDER, A TUBULAR PISTON SLIDABLY RECEIVED WITHIN SAID CYLINDER, AND AN INNER PISTON SLIDABLY RECEIVED WITHIN SAID TUBULAR PISTON, SAID INNER PISTON HAVING AN OUTER DIAMETER SUBSTANTIALLY THE SAME AS THE INNER DIAMETER OF THE TUBULAR PISTON, AND 